Chronic rhinosinusitis is a major health problem that affects approximately 15% of the US population. It is the hypothesis of this Program Grant that chronic rhinosinusitis represents a disease of epithelial cell and mucosal dysfunction. Together the 3 Projects that comprise this program provide an integrated approach to evaluate if this epithelial dysfunction arises as a result of an inherent genetic defect(s), environmental influences, or a combination of the two. This CORES serves as an essential clinical resource and will provide support for each of the 3 projects by pursuing the following aims: We will recruit and characterize the chronic rhinosinusitis patients that are required by all of the Projects, as well as the healthy, normal subjects and patients with perennial allergic rhinitis that are required as control populations for the second and third projects. We will assist the second project in ensuring the aggressive follow up of subjects recruited to assess the role of viral infections in the induction and recurrence of chronic rhinosinusitis; and of corticosteroids in reducing disease recurrence after surgery. We will also provide the sinus mucosal biopsies required as part of this protocol. We will assist the first Project in surveying, by questionnaire, members of families that have inherited a mutation in the cystic fibrosis transmembrane regulator (CFTR), and will clinically characterize family members with a positive history to verify that they have chronic rhinosinusitis. Enrollment of these family members will also serve the needs of the third Project. We will clinically characterize obligate carriers of CFTR mutations (i.e. parents of cystic fibrosis patients), recruited by the first project who have a positive history by questionnaire to verify that they have chronic rhinosinusitis. We will continue to maintain, refine and update a relational database that is being used to record demographic and clinical information on patients with chronic rhinosinusitis who are recruited into our studies. The use of well characterized patients is critical to any attempt to examine the pathogenesis of chronic rhinosinusitis, or to test therapies that may improve the management of this disease.